The present invention pertains to a hydraulic control system for a hoisting winch, such as that of a mobile crane, and particularly for a reversible winch of the type having a spooling drum driven by a bidirectional hydraulic motor via planetary reduction means.
A hydraulic crane winch is known wherein the cable drum is driven by a bidirectional hydraulic motor via planetary gear drives connected in series, with the drum carried by the internal or ring gear of the final planetary gearing. A spring-loaded brake normally arrests the rotation of the planet carrier of the final planetary gearing, permitting the drum to rotate with the ring gear for the hoisting or controlled lowering of the load carried by the winch. The brake is released hydraulically, whereupon the drum becomes freewheeling, allowing the free fall of the load. The fluid pressure actuation of the brake is required only for the freewheeling of the drum.